We proposed to evaluate kidney function in three different strains of genetically hypertensive rats, comparisons to be made both between the different strains and between each strain and its appropriate normotensive control strain. To differentiate between renal functional differences which precede hypertension and may be causal in nature, and differences which secondarily result in response to hypertension, studies will be carried out in weanling, adolescent and adult rats. Because the kidney regulates blood pressure both through control of fluid balance and by producing vasoactive hormones, a variety of experimental protocols will be used. 1) In anesthesized rats, we will study the relation between renal perfusion pressure and renal blood flow--glomerular filtration rate; included will be effects of changes in perfusion pressure before and during vasodilator infusion. 2) Isolated, perfused kidneys will be used to determine the relation of age to the vascular response to norepinephrine, prostaglandin release in response to norepinephrine, and the renal capacity to convert arachidonic acid to prostaglandins. 3) Changes in systemic blood pressure, age, and segmental resistance will be comparatively studied in the renal and mesenteric vasculature. 4) In metabolic studies of water and electrolyte balance, we will determine sodium retention; in addition, urinary prostaglandin, aldosterone, and kallikrein output will be measured. 5) Control of renal prostaglandin metabolism will be studied as a function of ages. Cortex, medulla and papilla homogenates will be assayed for prostaglandin synthetase, dehydrogenase and 9-ketoreductase activity. The possible presence of inhibitors of each will be tested. 6) The effect of chronic suppression of prostaglandin synthesis on blood pressure development will be determined.